Effective processing of corn germ into both food and feed grade products can enhance the long-term viability of the corn ethanol industry and can prove to be a lucrative business opportunity in itself. Defatted corn germ flour is a byproduct of the corn oil industry that is typically used as an ingredient in animal feed. The problem in developing corn germ as a protein-rich product for human consumption relates to the deterioration of the corn germ during extended periods of storage. Such deterioration is caused by conventional pressing methods and solvent extraction methods that leave lipids in the corn germ flour that enzymatically oxidize into compounds that contribute a bitter flavor.
The term “corn germ” is used throughout this application to refer to “dry fractionated corn germ” as opposed to another distinctly different product “wet-milled corn germ” or “wet fractionated germ”.
The corn kernel is comprised of a number of components, each having a different nutritional composition and commercial use. The major parts of the corn kernel are the pericarp/tip cap, germ, and endosperm. The pericarp/tip cap is high in fiber, while the germ has a high protein and oil content. The endosperm contains most of the starch. The corn germ, representing 11% of the corn kernel by weight, contains the genetic information for the seedling as well as enzymes, vitamins and minerals. The composition of the corn germ is approximately 33% oil, 18% protein, and 18% fiber with the balance being sugar, starch, and ash.
Two basic methods are employed in processing corn kernels. The processes are known as “wet-milling” and “dry-milling.” Wet-milling is a method by which the corn kernel is separated into starch, germ, fiber, and gluten by steeping the corn kernel in a solution prior to grinding and centrifugation to separate the components of the corn kernel. The solution in which the corn kernel is steeped generally contains sulfur dioxide and enzymes, such as lactic acid. Such solution renders the corn flour obtained from the wet-milled corn kernel inadequate for human consumption. As such, corn flour obtained from wet-milling is typically used in animal feed. Lucisano et al. [J. Food Sci. 49:482-484 (1984)] states that wet-milling produces a product that is unsuitable for human consumption as corn germs are modified during steeping. However, the study also states that the dry-milling process provides a product that is adequate for human consumption.
Dry-milling is a process in which the entire corn kernel is cleaned, and then water is added to increase the moisture content. The corn kernel is tempered to allow the moisture to spread throughout the grain. The moisture allows the germ to toughen for easy removal. In the dry-milling process, the germ is removed from the endosperm early. The remaining parts of the corn kernel are ground and sieved into various fractions.
The majority of corn in the United States is used whole, either as animal feed or is fed into ethanol plants. However, individual components of the corn kernel provide far greater value than used as a whole. As such, fractions have been separated by wet and dry corn millers, and an increasing number of ethanol plants are contemplating installing fractionation processes to take out the bran and germ prior to processing the corn for fermentation.
Although the amount of corn germ extracted has increased, there is a shortage of plants to process the corn germ into food-grade oil and meal. Such shortage is due to the absence of a method by which food-grade oil and meal can be efficiently and affordably produced. Currently, 450 to 800 tons of corn germ is obtained from various suppliers each day. More suppliers are projected to arise as existing dry mill ethanol facilities consider installing a technology called Dry Corn Fractionation. There are on the order of 200 corn ethanol plants in the US with a combined ethanol production capacity on the order of 13 billion gallons per year. These plants consume some 4.8 billion bushels of corn per year. These 4.8 billion bushels contain 8-10% readily extractable corn germ through the use of dry fractionation processes. Total quantity of extractable corn germ is on the order of 12 million tons per year, an amount that is more than adequate to supply a substantial sized corn germ processing industry. Such a supply has the potential for being processed into a great deal of food-grade corn oil and flour if an efficient method for producing food-grade defatted corn germ flour is determined.
Through the process for obtaining food-grade corn germ flour from dry fractionated corn germ, crude food-grade corn oil is also obtained. Corn oil is in high demand due to increasing consumer preference for oils without trans fats. It is the second most produced vegetable oil in the United States and is considered “healthy oil”, with no cholesterol. While the supply of dry fractionated corn germ has increased, the production of food-grade corn oil has not increased as methods for producing food-grade corn oil have proven to be slow and costly. Thus, there is a need for a process that can produce food-grade corn oil in a manner that is cost effective and efficient.
A process for increasing corn oil extraction is provided in Published Patent Application No. US 2008/0260902 A1. The patent application teaches a process for utilizing the entire corn kernel to produce corn oil. As a result of the process a de-oiled corn meal is obtained. The extracted corn oil is used to make nutritionally enhanced food-grade corn oil, lubricants, biodiesel, and fuel among other products as stated in the patent application. The corn meal obtained from the process, however, may be useful in producing animal feed rations, snack food, cosmetics, and fermentation broth additive among other products. The patent application focuses on teaching a method for maximizing corn oil extraction from corn kernels as opposed to producing a nutrient rich corn flour for human consumption. Furthermore, the patent application does not teach a nutrient rich food-grade defatted corn germ flour comprising an amino acid profile reaching recommended nutritional values.
Feed-grade defatted corn germ meal, typically obtained from a wet-milling process, is currently sold as animal feed with a valuable protein and mineral composition that has a number of advantages for local livestock producers, particularly hog and dairy producers. Due to the protein and mineral composition of the defatted corn germ meal, it can replace up to 55% of a hog's diet. Using a defatted corn germ meal value of 100% of corn price and replacing 30% of the diet for a market hog would result in a feed cost savings of $6.30 to $28 per ton of feed and an incremental profit of between $5 and $8 per market hog. For the average pork producer feeding 6,000 head per year, that equates to a savings of $30,000 per year. Great nutritional and economic benefits have been observed from feeding corn germ meal to animals. Similarly, defatted corn germ meal, a high protein product, has promise as a human food ingredient.
For food-grade corn germ flour, defatted corn germ meal is ground into fine flour with the use of a 200-mesh screen. This product is not being produced on a commercial scale because the oil is too expensive and slow to extract from the corn germ according to dry fractionation. Thus, on the commercial scale, wet-milling typically processes defatted corn germ. Wet-milling efficiently produces food-grade corn oil but results in a feed-grade defatted corn germ flour due to the addition of enzymes, which render the product inadequate for human consumption.
Addition of defatted corn germ flour enhances the nutritional value of diets, especially when added to bakery goods. A study regarding the composition of three food products containing defatted corn germ flour, Blessin et al. [J. Food Sci. 38:602-606 (1973)], taught that by adding defatted corn germ flour to cookies and muffins, starch content is decreased and protein content is increased. As to the third food product, beef patties, there was very little nutritional impact by adding defatted corn germ flour. Tsen et al. [Cereal Chem. 51:262-271 (1974)], further supported the finding in Blessin that adding defatted corn germ flour to bakery goods provides nutritional fortification. Tsen taught that acceptable bread could be prepared from wheat flour fortified with 12% defatted corn germ flour. Thus, both studies found that bakery goods of various types can be fortified with enough defatted corn germ flour as to ensure nutritive improvement and is a simple modification that can be easily incorporated to enhance the diet of individuals.
Due to the significant nutritional value of defatted corn germ flour, it can be an appropriate addition to the diet of third-world countries. By adding one cup of defatted corn germ flour to two cups of a starch product, such as rice, an undernourished population can receive full, recommended, nutritional intake. Furthermore, defatted corn germ flour may also be utilized in middle-eastern diets as the corn germ flour produced is Kosher. In addition to nutritional considerations, the functional properties of defatted corn germ flour, such as emulsifying properties, foaming capacity and stability, water and oil absorption and solubility also contribute significantly to the final quality of a processed food product.
In the art of producing food-grade defatted corn germ flour, little success has been achieved in using a solvent-extraction method for producing food-grade defatted corn germ flour on a commercial scale due to lack of efficiency, economics, and quality of product. Producing a food-grade product by de-fatting dry-milled corn germ with carbon dioxide under supercritical conditions is taught by U.S. Pat. No. 4,495,207. The invention teaches an alternative method to producing food-grade corn germ flour as conventional pressing methods and solvent extraction methods using hydrocarbons have been found to yield an unpalatable product due to enzymatic oxidation of lipids remaining in the corn germ meal subsequent to extraction.
In addition to concerns regarding the enzymatic oxidation of residual lipids, solvent-extraction methods have also posed concerns on the nutritional and functional quality of proteins in the defatted corn germ meal. Barbieri et al. [J. Food Tech. 18:35-41 (1983)] teaches that conditioning the corn kernel prior to removing the corn germ and conditioning the flaked corn germ prior to solvent-extraction substantially decreased protein solubility, while protein digestibility remained substantially constant.
In light of the forgoing prior art, it is evident that an efficient and cost effective method for producing food grade defatted corn germ flour would be greatly beneficial to improve individuals' diets, as the positive nutritional benefits of defatted corn germ meal are well established. Production of defatted corn germ flour on a commercial scale can prove to be beneficial for individuals seeking to add greater nutrients to their diet. If produced efficiently, the affordability of the defatted corn germ meal would provide a great cost to nutrition ratio, especially for undernourished individuals in third-world countries.